Usually, if you wanted to create a beautiful but complex font for your game, you would have to make a font atlas in photoshop (or similar), add whatever effects you want, save it and then use it in your game.
Atlasses take up a ton of space on the disk and memory in RAM. It's also difficult to tell which ones you will need (for example, for numbers you may only need to create digits, so do you leave out all letters and symbols &%!$# ? What about diacritical marks?). Also, you need to decide what size your atlas should be (HD or low-res). Dealing with distance field fonts is a pain, so what can you use instead?
FontEffects helps you to generate nice fonts on the fly in-game. Feed the library a picture of a letter in any size from FreeType (or any other image) and you'll get a beautiful symbol on return. All of this is done with only a couple of lines of code. The library is written in C++, is lightweight, available on the MIT license, doesn't depend on other libraries and has a simple C interface.
That's where the visual editor comes in. It doesn't use generic filters like Photoshop (Stroke/Glow/Fill), but instead takes advantage of a fully-featured graph editor that can produce image of any complexity.
Video Example:
Here is an example of a saved project in the editor (and the file that you load in the game):
FEF2
#sigma
size:100
distance:1.05
@nodes
*1,1,0,0,0,10,10,0,0,0,0,0,0,0,0,
*50,2,0,0,0,579,21,0,0,0,0,1,0,0,0,
*3,4,0,4,4,144,166,0,0,0,0,0,0,0,0,
3,000000FF,0,FFFFFFFF,.7031,FF8787FF,1,1,FF,0,.5286,.8489,33.7156,1.6017
*3,3,0,0,0,145,10,0,0,0,0,0,0,0,0,
2,FF0000FF,.3691,00FF89FF,1,1,FF,0,0,1,0,1
*10,5,0,0,0,148,345,1.75,0,0,0,0,0,0,0,
*6,6,0,0,0,360,258,10,0,0,0,0,0,0,0,
*5,7,0,0,0,355,63,0,0,0,0,0,0,0,0,
*3,8,0,0,0,533,247,0,0,0,0,0,0,0,0,
2,01B4FFFF,0,000000FF,1,2,00,.4707,FF,.5273,0,1,0,1
@edges
*7,2,1
*8,2,4
*1,4,3
*1,3,3
*1,5,3
*7,6,2
*3,7,1
*5,7,2
*4,7,4
*6,8,2
Here's pseudocode demonstrating how to work with the library: https://github.com/frankinshtein/font-effects-lib/blob/master/test/main.cpp
#include "fe/fe.h"
...........
// load effects from buffer into memory
fe_bundle* bundle = fe_bundle_load(buff, size);
// get the effect by name (the file may contain different ones)
fe_effect *effect = fe_bundle_get_effect_by_name(bundle, "sigma");
// get the final node
fe_node *out_node = fe_effect_find_node_by_type(effect, fe_node_type_out);
// get the source image (parameters below are taken from the FreeType structs)
int bitmap_left = 0;
int bitmap_top = 0;
int src_width = src_image.w;
int src_height = src_image.h;
int pitch = src_image.pitch;
const void *data = src_image.data;
FE_IMAGE_FORMAT src_format = FE_IMG_R8G8B8A8; //use FE_IMG_A8 with freetype
int font_size = 100;//FT_Set_Pixel_Sizes(_face, 0, font_size);
fe_im result;
// key lines, apply our effect to the image
bool ok = fe_node_apply(font_size,
bitmap_left, bitmap_top,
src_width, src_height,
src_format, pitch, data,
out_node, &result);
// upon return, result is a buffer with the image - you can now use it for whatever you need!
Emscripten Web Demo: http://oxygine.org/font_effects/HelloFreeType.html